Britain's Prince Philip, who turns 95 on Friday, has been Queen Elizabeth II's constant companion for almost 70 years, offending and amusing in equal measure with his salty off-the-cuff comments and gaffes.

Known formally as the Duke of Edinburgh, the prince is a supporter of numerous charities and has been a reassuring presence at Elizabeth's side.

A self-described "cantankerous old sod", Philip's unvarnished humour endears him to some but often makes headlines for the wrong reasons.

In 2015 he was caught on camera appearing to tell a photographer "just take the fucking picture!" and asked a group of unpaid community workers: "Who do you sponge off?"

"You managed not to get eaten, then?" was one typical remark to a British student who had trekked in Papua New Guinea in 1998.

And on a historic state visit to China in 1986, Prince Philip warned a group of British students: "If you stay here much longer, you'll all be slitty-eyed."

Although garnering a reputation for coldness towards his children, the prince is considered by observers to be the glue that held the royal family together during a series of divorces by three of his four offspring.

In a rarely seen softer side, it emerged that the late Princess Diana addressed him as "Dearest Pa" in letters in which he offered solace over her deteriorating marriage to his eldest son Prince Charles.

- Exile from Greece -

The prince has been largely blessed with robust health, but was admitted to hospital with various complaints as he advanced into his 90s.

He suffered a bladder infection during the queen's diamond jubilee celebrations in 2012 and had a coronary stent fitted in 2011.

However, he accompanied the queen on overseas visits as recently as 2015, although was forced to miss a World War I commemorative ceremony last month on "doctors' advice".

Never one to talk about his own feelings, the prince admitted in a rare interview that he had carved out his own role by "trial and error".

Asked if he had been successful, he told the BBC: "I couldn't care less. Who cares what I think about it? I mean it's ridiculous."

But the queen was more forthcoming, calling him "my strength and stay all these years" in a golden wedding anniversary speech in 1997.

Prince Philip was born on a kitchen table on Corfu on June 10, 1921, the only son of Prince Andrew of Greece -- the younger brother of Greece's King Constantine -- and Princess Alice of Battenberg.

Aged just 18 months, he and his family were evacuated in a British Royal Navy ship from politically unstable Greece, with the toddler reputedly carried in a cot made from an orange box.

The family settled in Paris, sending the young Philip to preparatory school in England when he was just seven, then secondary school at Gordonstoun in Scotland, where he was head boy.

- Duty to serve -

He became a Royal Navy cadet following the outbreak of World War II in 1939, before serving on battleships in the Indian Ocean and the Mediterranean.

By 1945, he was a first lieutenant and witnessed the Japanese surrender in Tokyo Bay with the British Pacific Fleet.

Philip and the then Princess Elizabeth, the future queen, were formally introduced in July 1939 when her father King George VI and his family toured the Royal Naval College in Dartmouth, on England's south coast.

They kept in touch during the war and met on a number of occasions. But it was not until July 1947 that their engagement was announced and they tied the knot that year on November 20 at London's Westminster Abbey.

Prince Philip's naval career was cut short after his wife ascended to the throne following the death of King George VI in 1952, but said "being married to the queen, it seemed to me that my first duty was to serve her in the best way I could".

In his spare time he is a keen horseman, competing at international level for Britain in the sport of carriage-driving.

He has also been patron of a number of organisations, including the WWF conservation group, and chancellor of the universities of Cambridge and Edinburgh.